Effect of post-heat treatment on the UV transmittance, hydrophobicity, and tensile properties of PVA/Uncaria gambir extract blend films.

The physical and mechanical properties of biopolymers can be improved by heating technologies. In this research, we improved the properties of Polyvinyl alcohol (PVA)/Uncaria gambir extract (UGE) blend films by post-heating method. After post-heating, the blend film exhibited higher resistance to UV light and improved contact angle performance, while water vapor permeability and moisture absorption decreased. The tensile strength and toughness of the PVA/UGE blend film with a post-heating duration of 40 min were 68.8 MPa and 57.7 MPa, respectively, an increase of 131 % and 127 %, compared to films without post-heating. This facile and cost-effective fabrication method, with environmentally friendly properties, can be applied to biodegradable PVA/UGE blend films to achieve desired properties for optical devices or food packaging materials.

A Novel Highly Conductive, Transparent, and Strong Pure-Cellulose Film from TEMPO-Oxidized Bacterial Cellulose by Increasing Sonication Power.

Developing a conductive cellulose film without any metal compounds remains challenging, though in great demand. However, cellulose film prepared from bacterial cellulose (BC) powder without any metal compounds has poor tensile, physical, and electrical properties, thus limiting its application. Herein, this study aims to prepare and characterize an all-cellulose film from 2,2,6,6-Tetramethylpiperidin-1-yl)oxyl (TEMPO)-oxidized bacterial cellulose (TOBC) powders without adding metal compounds and treated by ultrasonication. TOBC powders are sonicated with various powers of 250, 500, and 750 W for 20 min without any other substance. It was proved that increasing the ultrasonication power level resulted in a significant improvement in the properties of the film. The ultrasonication of 750 W increased tensile strength by 85%, toughness by 308%, light transmittance by 542%, and electrical conductivity by 174% compared to the nonsonicated film. A light-emitting diode connected to a power source through this sonicated film was much brighter than that connected via a nonsonicated film. For the first time, this study reports the preparation of electrically conductive, transparent, strong, and bendable pure TOBC films by increasing ultrasonic power for environmentally friendly electronic devices application.

Highly antimicrobial and strong cellulose-based biocomposite film prepared with bacterial cellulose powders, Uncaria gambir, and ultrasonication treatment.

This work characterized bacterial cellulose (BC)/Uncaria gambir (G) biocomposite film prepared with ultrasonication treatment. Films were prepared from BC powder suspensions in distilled water without and with various loadings (0.05 g, 0.1 g, 0.2 g, 2 g) of G powder then treated using an ultrasonic probe at 1000 W for one hour. The results revealed that the ultrasonication treatment of the suspension greatly increased tensile strength (TS), elongation at break (EB), and toughness (TN) of a BC film by 3097%, 644%, and 32,600%, respectively, compared to non-sonicated BC film. After adding 0.05 g G into the sonicated BC powder suspension, TS, EB, and TN of the biocomposite film were improved to 105.6 MPa, 14.3%, and 8.7 MJ/m3, respectively. The addition of the G increased in antimicrobial activity of the film. This study indicates that biocomposite film is potentially useful for nanopaper production with good antimicrobial and high tensile properties.

Effect of heat treatment on thermal resistance, transparency and antimicrobial activity of sonicated ginger cellulose film.

Transparent film with high thermal resistance and antimicrobial properties has many applications in the food packaging industry particularly packaging for reheatable food. This work investigates the effects of heat treatment on the thermal resistance, stability of transparency and antimicrobial activity of transparent cellulose film. The film from ginger nanocellulose fibers was prepared with chemicals and ultrasonication. The dried film was heated at 150 °C for 30, 60, 90, or 120 min. The unheated and sonicated film had the lowest crystallinity index and the lowest thermal properties. After heating, the film became brownish-yellow resulting from thermal oxidation. The reheated film had higher thermal resistance than unheated film. Heating led to further relaxation of cellulose network evidenced by shifting of the XRD peak positions toward lower values. The antimicrobial activity decreased due to heating. Average opacity value increases after short heating durations. It was relatively stable for further heating.

Characterization of disintegrated bacterial cellulose nanofibers/PVA bionanocomposites prepared via ultrasonication.

With the increasing demand for simple, efficient, environmentally friendly preparation methods to produce cellulose nanofibers for reinforcing a biodegradable film is increased, the role of nanofibers from the pure cellulose produced by bacteria becomes more important. This work characterized bacterial cellulose nanofibers disintegrated using a high shear homogenizer. These nanofibers, in 2.5, 5, and 7.5 mL suspensions, were mixed with PVA gel using ultrasonication. The resulting dried bionanocomposite film was also characterized. Adding nanofiber significantly increases (p ≤ 0.05) on tensile strength, thermal resistance, water vapor impermeability, and moisture resistance of PVA film but not strain at break. Tensile strength, tensile modulus, and elongation at the break of the 7.5 mL nanofiber reinforced film were 37.9 MPa (increased by 38%), 547.8 MPa (increased by 26%), and 10.7% (decreased from 17.2% for pure PVA), respectively compared to pure PVA. Transparency decreases slightly with increased nanofiber content. These properties indicate that this bionanocomposite film has potential in food packaging applications.

Characterization of PVA/cassava starch biocomposites fabricated with and without sonication using bacterial cellulose fiber loadings.

This paper reports the characterization of polyvinyl alcohol (PVA)/cassava starch biocomposites. The cassava starch gel with or without ultrasonic probe treatment was mixed with PVA gel then short bacterial cellulose fibers were added. The presence of the sonicated starch gel in the PVA resulted in low thermal and moisture resistance, and low transparency of the blend film. After adding the fibers thermal and moisture resistance of the sonicated biocomposite increased due to stronger hydrogen bonding between the fibers and the matrix. Tensile strength of sonicated biocomposite with 10 g fibers increased 215% compared to the sonicated blend. However, addition of the fibers to the non-sonicated blend did not significantly increase mechanical and thermal properties or moisture resistance of the biocomposite. Opacity of the non-sonicated biocomposite was lower than that of the sonicated one.

Effect of nanofibers fraction on properties of the starch based biocomposite prepared in various ultrasonic powers.

This paper reported the results of the characterization of jicama (Pachyrhizus erosus) starch based biocomposite reinforced with varied nanofiber fractions, i.e. 35.4, 70.8 and 106.2 µg per 10 g of starch. The nanofiber was isolated from oil palm empty fruit bunches. During preparation, the biocomposite in form of gel was sonicated using an ultrasonic probe at various powers, i.e. 0, 480, 600, 720 watt at 20 kHz for 5 min. The results show that ultrasonication results in a significant improvement in biocomposite properties for each of the nanofiber fractions. The tensile strength, moisture resistance of the 35.4 µg nanofibers biocomposite increase significantly 278, 11% respectively after 600 watt ultrasonication. Field emission scanning electron microscopy of the fracture surface of the film showed ultrasonication resulted in it becoming smoother and more compact. These results indicate that ultrasonication improves the performance of the film.

Preparation of nano-sized particles from bacterial cellulose using ultrasonication and their characterization.

As more applications for nano-sized natural particles are discovered, simple, environmentally friendly ways to produce these particles become more important. This work prepares and characterizes nano-size bacterial cellulose particles using ultrasonication. Pellicle from nata de coco containing nanofibers was broken up in an electrical blender, then sonicated using an ultrasonic probe at 20 kHz and 3 W/mL for 30, 60 and 90 min. Transmission electron microscope observations indicate the particles become nano-sized after 60 min ultrasound. The maximum decomposition temperature before sonication was 373 °C, decreased to 357 °C after 60 min ultrasonication. Moisture absorption of the 90 min sonicated particles film is 60% slower compared to non-sonicated particles. After ultrasonication, the crystallinity index of the cellulose decreases. The functional groups of non-sonicated and sonicated cellulose remain the same. This study promotes a potential method of fabrication of nano-sized particles from pure bacterial cellulose.